Communication systems typically have multiple end units able to receive and/or transmit audio signals. The audio signals received and/or transmitted by and/or to the end units of a communication system may be voice signals from users of the communication system. Communication systems may be analogue and/or digital, wherein the communication systems are configured to transmit analogue and/or digital audio signals. Communication systems can be either wired or wireless. Wireless communication systems allow for the transmission of audio signals between the various components of a communication system without having to also connect the communication system components with wires to carry the audio signals. Wireless communication components may transmit audio signals between the wireless communication systems in analogue and/or digital format.
Digital voice communication systems may typically convert speech signals from a user of the communication components into digital signals. These digital signals may then be transmitted via radio or over wires from one point on the digital voice communication system to another. The speech from the user may be received by the communication system component through a microphone associated with the communication system component used by the user, the transmitting communication system component. The microphone may convert the speech into a signal representing the speech, and the signal representing the speech may be digitized into digital data. The digital data may be transmitted from the transmitting communication system component to a receiving communication system component. At the receiving communication system component, the digital data may be converted back to a signal representing the speech of the user. The signal representing the speech may be sent to a speaker near a second user of the digital communication system, and the speaker may convert the speech signal into speech audible to the second user.
Digital signals may be transmitted with less degradation than analogue signals because digital communication systems are often simpler and easier to implement than equivalent analogue systems. Data representing speech must be transmitted serially. When raw digitized speech is transmitted serially, the data rate can be so high that channel spectral efficiency is poor. It is thus advantageous to process the raw digitized speech to reduce the data rate prior to transmission.
Typical digital voice communication systems use encoders and/or decoders to encode and/or decode digital audio signals. The encoders and/or decoders may also reduce the amount of data that is to be transmitted, thus saving spectrum bandwidth.
The transmitting communication system component may digitize the speech signal and then encode the speech signal into encoded digital speech signals for digitally transmitting to the receiving communication system component. The receiving communication system component may decode the encoded digital speech signals back to digitized speech signals, which may then be converted to analogue audible speech signals for transmission by the receiving communication system component.
Encoding and decoding digital speech signals is typically performed by voice encoders (vocoders) or coder/decoders (codecs). As used herein, the term codec will be used to refer to codecs, vocoders, and/or other encoders and/or decoders. For the encoded digital speech data transmitted by the transmitting digital communication component to be decoded by the receiving digital voice communication component, the codecs used by the transmitting and receiving digital voice communication components must agree on the type of encoding to use and the transmission data rate.
Digital voice communication components typically contain a codec for encoding and/or decoding speech. Typically, each of the communication components in a digital voice communication system must contain the same type of codec. Due to codecs being configured to process speech signals in individualized ways, different types of digital voice communication components having different codecs are typically incompatible.